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Date:      Fri, 10 Dec 2010 10:38:28 +0100
From:      Ivan Voras <ivoras@freebsd.org>
To:        freebsd-hardware@freebsd.org
Subject:   Re: Poor / buggy performance with the mpt driver in 8.1 AMD64?
Message-ID:  <idssel$bq8$1@dough.gmane.org>
In-Reply-To: <AANLkTinVc9zKzeiEBGf1hF9yq=AQw4Ve=8o7ZfZ5pwKt@mail.gmail.com>
References:  <AANLkTinVc9zKzeiEBGf1hF9yq=AQw4Ve=8o7ZfZ5pwKt@mail.gmail.com>

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On 12/08/10 23:02, Mattias Lindgren wrote:
> I have 8 Seagate SATA disks connected to an intel branded LSI 3081E
> SAS controller (Intel SASUC8I).  I have 4 of the 1.5T disks and I have
> 4 2T disks (both are the LP 5900RPM variety) in a pair of raidz1s in a
> ZFS pool.  Doing simple dd writes and reads I get about 80MByte write
> and 150MByte read which seems very very slow to me.  I'm also getting
> errors from mpt on boot:

Such large difference between read and write, together with the slow 
rotation speed of your drives could indicate that you have 4K sector 
drive. Can you confirm this? (report what "diskinfo -v <drive>" outputs, 
but you'll probably also have to lookup on the drives themselves or on 
the net for the specific model you have).

If so, until FreeBSD gets this right (heh), you will have to do this 
dance with your drives to make ZFS 4K-aligned. But first, try figuring 
out if the drives are 4K.




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